4-8 October 2015
Hans Harnack Haus
Europe/Berlin timezone
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Contribution Poster (WITHDRAWN)

Poster session

Porosity and band-strengths measurement of multi-phase composite ices using mid-infrared optical constants and extended effective medium approximations


  • Dr. Jean-Baptiste BOSSA

Primary authors



Remote observations of star forming regions performed by space telescopes have provided the full inventory of interstellar ice components and the abundances of these constituents are deduced from acurate optical constants and reference spectra in the mid-infrared. Starting from this principle, our main goal is to characterise how the amount of pores and the abundance of a contaminent (e.g., CH4) affects the mid-infrared optical constants of a porous composite ice dominated by water. Depending on the amplitude of the alteration, this investigation holds the potential to determine the porosity and the band-strengths of multi-phase composite ices. As one can expect, the first difficulty to face is the countless possible combinations involving pores, water, and methane. Since it seems to be impossible to determine experimentally the whole set of optical constants, the use of a theoretical treatment is therefore required for each case. Based on effective medium approximations, namely Maxwell-Garnett and Bruggeman, we first calculate the effective mid-infrared optical constants of a large set of fictive porous H2O:CH4 ices. Then, we compare the whole effective data set with experimental values obtained from the mid-infrared spectra of ices grown in the laboratory with known thicknesses and relative abundances.